Dr. Ruan is widely recognized for his research in biomass and solid waste conversion, including plastic waste pyrolysis and gasification for the production of chemicals, materials, fuels, and energy. His work extends to innovative wastewater treatment solutions, airborne pathogen disinfection, catalytic non-thermal plasma, microwave and photocatalytic technologies, and food engineering advancements. His research has resulted in significant contributions to engineering knowledge, with over 43,000 citations, an h-index of 106, and an i10-index of 531. Dr. Ruan is also a Fellow of National Academy of Inventors (Class of 2023), and a Fellow of the American Society of Agricultural and Biological Engineers (ASABE) and the Institute of Food Technologists (IFT). Most recently, Dr. Ruan was elected to the National Academy of Engineering (Class of 2025).